Pedal assembly for an automotive vehicles

ABSTRACT

The present invention relates to a pedal assembly (1), useful in automotive vehicles includes an accelerator pedal (6), a brake pedal (7) and a clutch pedal (8), each of the three pedals (6, 7 and 8) actuating an associated, electronically controlled device (potentiometer 9, 10; switch 11), the said pedal assembly (1) being pre-assembled and being connectible via electric connections with an energy supply unit (2) and a data bus (4). 
     The present invention affords a pedal assembly (1) which lends itself to ease of mounting and manages without splashboard apertures in the pedal area. Further, this pedal assembly (1) satisfies the demands of modern industrial production such as modular type of construction or just-in-time supplies.

The present invention relates to a pedal assembly for automotivevehicles. Such pedal assemblies are generally known as they areinstalled e.g. in all automotive vehicles nowadays. Usually they arecomposed of two or three pedals for accelerating, braking and coupling,there being no need for the latter in cars with automatic transmission.The state-of-the-art pedals are coupled to a generating cylinder bymeans of lever assemblies for instance. Partly, the pedal positions arealso converted into electronic signals, for instance as regards theaccelerator pedal of a vehicle with a fuel-injection engine.

The customary pedals are mounted individually into the automotivevehicle which is expensive and time-consuming. Besides, hydraulic linesmust be fitted to extend through the entire vehicle. Further, thesplashboard isolating the engine compartment from the passenger cabinmust be penetrated several times.

Therefore, the present invention is based on the object to provide apedal assembly which lends itself to ease of mounting and which manageswithout apertures in the splashboard in the pedal area. Further, thepedal assembly according to this invention is desired to conform to thedemands of modern industrial production such as modular type ofconstruction or just-in-time supplies and to permit an intelligentprocessing of the arising signals.

This object is achieved by the features set forth in the main claim. Ofcourse the subject matter of this invention can be used also onautomotive vehicles with automatic transmission and, in this event,requires only an accelerator pedal and a brake pedal.

The data-processing stage can be of redundant design for safety reasons.It processes the signals produced by means of the pedals and rendersthem appropriate for a data bus. The structure of a possibledata-processing stage is illustrated in FIG. 1 and will be described inmore detail in connection with the description of the Figures.

When the signal processing is redundant, it is particularly expedientthat each pedal generates at least two pedal-position signalsindependently of one another.

Ease of assembly of the resent invention can be enhanced by theapplication of the features to be gathered from claim 2.

According to another improvement of this invention, each pedal producestwo signals representative of the exact pedal position as well asanother signal indicating that a threshold value is exceeded. That is tosay, once the two first signals differ from one another--due to an errorin the system--it is possible by virtue of the additional thresholdvalue signal to decide whether a pedal is applied or which one of thetwo first signal generators issues correct signals.

The pedal-position signals can be generated in a particular simplefashion by means of rotary potentiometers. This possibility which isdescribed more precisely in claims 7 to 9 will be explained by way ofFIGS. 3 to 5.

According to an improvement upon the present invention, at least oneleaf spring cooperating with stops is provided below the foot board.This measure permits to adjust the force-travel characteristics knownfrom conventional pedals also on the pedal assembly according to thisinvention. Without these stops the linear force-travel characteristiccurve is obtained which is usual with springs.

Each pedal becomes particularly comfortable when an adjustable supportis provided in the heel area. In order to be able to adapt the pedalassembly to the foot inclination which varies depending on the driver'sheight, another improvement arranges for the pedal inclination to beadjustable.

Favourably, the adjustment mechanisms are electrically operable sincethe pedal assembly is scarcely accessible beneath the steering wheel andthe instruments panel for a mechanic direct adjustment. If the vehicleis equipped with a seat-memory function, the adjustment mechanisms canbe combined with it as well.

Possible embodiments of this invention will be explained in thefollowing by way of the accompanying drawings. In the drawings,

FIG. 1 is a schematic view of the data-processing stage of the pedalassembly,

FIG. 2a is a front view of one arrangement of the pedals of the pedalassembly,

FIG. 2b is a side view of the arrangement shown in FIG. 2a.

FIG. 3 is a cross-section of the pedal of FIG. 2b,

FIG. 4 is a cross-section of the pedal of FIG. 2a,

FIG. 5 is a cross-section of another pedal design,

FIG. 6 is a pedal assembly with modified pedals,

FIGS. 7 to 10 show details in respect of several pedals with differentsensors and/or converters in the pedal,

FIGS. 11 and 12 show the connection of one of the pedals according toFIGS. 7 to 10 with an emergency actuation of a brake.

In FIG. 1 the rectangle in phantom lines symbolizes the pedal assembly 1which is connected with an energy supply unit 2 and, via theintersection 3, also with a data bus 4 of the vehicle. The lines withinthe pedal assembly 1 are not referred to in detail, the data flow is ineach case illustrated by the direction of arrows.

A line leads to the unit 5 from the extraneous energy supply unit 2which, conventionally, is formed by the accumulator of the automotivevehicle. Said unit 5 comprises an auxiliary accumulator as well as astabilizer and furnishes all other construction elements with thenecessary energy. The auxiliary accumulator ensures that the pedalassembly 1 is able to deliver a warning to the driver even after failureof the energy supply unit 2, and in that the driver still has the timeto bring the vehicle to a halt.

The pedal assembly 1 includes an accelerator pedal 6, a brake pedal 7and a clutch pedal 8. Each of the pedals 6, 7, 8 operates twopotentiometers 9 and 10 as well as a switch 11. Said switch 11 isactuated as soon as the corresponding pedal 6, 7 or 8 exceeds a specificthreshold value of inclination. The signals of the potentiometers 9 aresupplied via the multiplex unit 12 and the analog/digital converter 13to the microprocessor 14 which is also furnished with the signals of allswitches 11. The signals of the potentiometers 10 are supplied via themultiplex unit 15 and the analog/digital converter 16 to themicroprocessor 17 which likewise is furnished with the signals of allswitches 11.

Data exchange takes place between the two microprocessors 14 and 17 andallows to check whether any one of the two data-processing branches isdefective. Owing to the redundant design of the pedal assembly 1, errorsare detected before the information of the microprocessors 14 and 17 isissued via the intersection 3 to the data bus 4. It can be determined bymeans of the switch signals also supplied to the microprocessors 14 and17 in which one of the data branches the error will be probably found.

FIG. 2a illustrates the pedal assembly 1 from the front while FIG. 2bshows the side of it. All three pedals 6, 7 and 8 are designed as footboard 18. Since accelerator pedal 6 and brake pedal 7 both are operatedby the right driver foot, they are placed close to one another and haveone joint heel support 19. Hence the driver is required to only turn hisfoot when moving from the accelerator pedal to the brake pedal orvice-versa. The clutch pedal 8, too, is equipped with a support 19 forthe heel.

One of the pedals 6, 7 or 8 is shown from the side in FIG. 2b. The foot20 of the driver is placed on the pedal 6, 7 or 8. It can be seen thatthe support 19 is adjustable by the amount s, and the inclination of thefoot board 18 is adjustable from the mid-position 21 into everydirection by the angle α. That is to say, the inclination is adjustablein total by the total angle 2α. The pedal assembly 1 can be adapted tothe height of the driver owing to these possibilities of adjustment. Thefinal positions of the adjustment zones are indicated in dot-dash linesin each case.

FIG. 3 shows a cross-sectional side view of the pedal 6, 7 or 8. Thefoot board 18 with the support 19 is coated by the pleated bellows 22which also connects it with the housing 23 of the pedal assembly 1. Thefoot board 18 bears against the abutment 24 on the housing 23 and isrotatably coupled to the housing 23 at the attachment 25. Besides, aleaf spring 27 having a variable hysteresis is articulated at the pointof articulation 26 of the foot board 18, the other end of which springis clamped in on the housing 23. The leaf spring 27 cooperates withhousing stops 28, the position of which permits to adjust theforce-travel characteristics of the pedal.

A traction rope 30 is secured on the free end 29 of the foot board 18and runs over a pulley 31 and is held tight by a tension spring 32. Saidtension spring 32 is hooked on a projection 33 of the housing 23. Thelength of the rope 30 and, respectively, the angle zone β by which thepedal can be depressed is dimensioned such that the pulley 31 performsjust about one rotation with full pedal travel. The pulley 31 isarranged on the same axis 34 like the potentiometer 9. By depression ofthe foot board 18 the pulley 31 is moved to rotate via the tensionedrope 30 and simultaneously turns the rotary potentiometer 9 which thusgenerates a signal corresponding to the pedal position. The free end 29of the foot board 18 as well as the leaf spring 27 are each drawn inphantom lines also for the depressed position.

In FIG. 4 the same pedal 6, 7 or 8 like in FIG. 3 is shown, however fromthe top, with the foot board 18 being drawn only in dot-dash lines andbeing quasi transparent. All parts are provided with the same referencenumerals like hereinabove. The redundant design can be seen, that meansall important parts are provided twice and operate independently of oneanother. The two potentiometers 9 and 10 are drawn to be of differentsize which symbolizes their different structure and is meant to avoidthat, e.g. due to aging, both potentiometers 9 and 10 differ from thenominal value to the same extent. In the event of differing deviationsdue to a different type of structure they can be any time calibratedmathematically anew by way of the microprocessors (FIG. 1).

FIG. 5 shows another pedal variant which represents some sort of abutton and, when actuated, imparts a similar feeling like mechanicsuspended pedals. The housing 35 is screwed to a base plate 36 of thepedal assembly 1. The potentiometer 9 which is designed as a rotarypotentiometer is likewise screwed to the housing 35. Said potentiometeris operated by a screwed rod 37 which has a winding and, on depressionof the cap 38, is moved to rotate by the guide tube 39 coupled with thecap. A bumper 40 is provided on the cap 38 and moves to abut on housing35 after the full pedal travel w. Further disposed between the housing35 and the cap 38 are the resetting spring 41 and the pleated bellows 42sheathing the pedal towards the outside.

The guide tube 39 is guided in the housing 35 by means of a sphericalsleeve 43 almost devoid of losses due to friction, it is equipped with asecond bumper 44 for abutment on the spherical sleeve 43 in the inactiveposition and, via the cam disc 45, is in connection with the rod 37 inorder to set it to rotate on actuation. This rotation is directlytransformed onto the potentiometer 9.

A redundant design is likewise possible in the pedal variant shown inFIG. 5. The switch 11 shown in FIG. 1 is realized in that an electriccontact 46 is designed on the housing 35 and a sliding contact 47 isdesigned on the guide tube 39 above the cam disc 45.

The inactive position is shown on the left, while the actuated positionis shown on the right hand side in FIG. 5.

FIG. 6 shows a modified pedal assembly 50 wherein a clutch pedal 51, abrake pedal 52 and an accelerator pedal are premounted on an assemblyplate 54. Of course a smaller or a larger number of pedals can also bemounted on the assembly plate 54. For instance, the clutch pedal can becombined with the accelerator pedal 53, e.g. on vehicles with anautomatic clutch. Further, the actuating condition of one single pedalcan likewise decide on whether and in what condition the vehicle isbraked or accelerated so that accelerator pedal and brake pedal can be

The pedal assembly comprises as a housing an elastic cap 55 which isattached to the assembly plate 54 by way of a fastening ring 56. Saidattachment can be effected, as is indicated in FIG. 6, by screwing, orby a catch-type lock, by cementing pr by any other type of fastening thefastening ring 56 or the cap 55 itself to the assembly plate 54.

One may imagine the elastic cap 55 to be a segment (calotte) of a rubberball, it having a cavity in its interior. Simultaneously, it is ensuredby appropriate forces that the elastic cap is subjected to the effect offorce towards its outer surface so that it yields elastically whenexposed to force applied to it from the outside. After this outsideforce is deleted, it will re-assume its former condition so that thetemporary deformation is removed again.

FIGS. 7 to 10 show possible embodiments of the pedals 51 to 53 in across-sectional view.

In FIG. 7 the elastic cap 55 in turn is retained on the assembly plate54 by the fastening ring 56. Associated integrally with the elastic cap55 is a circular bottom 57, which bottom 57 can be cast, welded or madeintegrally by die-casting with the cap 55. A sensor 58 is arranged in anopening in the bottom 57 sealed relative to possibly escaping pressurefluid. Said sensor comprises two possibly cast-in electric connections59, 60 which are provided with electrodes 62, 63 projecting into theinterior 61 of the elastic cap 65. Said interior 61 is filled at leastpartly by a block of electrically conductive rubber, the electrodes 62,63 projecting into the rubber block. The rubber is chosen such that itselectric conductivity depends on the pressure it is exposed to. Theelectrodes 62, 63 are placed such within the rubber block which entirelyor partly fills the interior 61 that the force exerted on the outersurface of the elastic cap 55 results in a maximum possible change inthe electrical behaviour of the rubber. This means that under certaincircumstances the two electrodes 62, 63 can be arranged spaced muchfarther from one another than is shown in FIG. 7.

Once the operator of an automotive vehicle applies with his/her foot aforce on the outer surface of the elastic cap 55, a correspondingpressure will be applied to the interior and hence to the rubber block61 of the pedal assembly what results in a corresponding change in thecurrent flowing through the connections 59, 60. This change in currentand hence change in resistance of the rubber block is a standard for thedeformation of the cap 55 exerted by the operator and thus for themagnitude of the control quantity demanded by the operator. This way avery simple unit allows to easily control e.g. the speed of the vehicle,the intensity of the braking operation or the coupling action. It islargely indifferent at what point of the cap the operator's foot makescatch as long as the pressure exerted and hence the deformation of thecap are of a sufficient amount.

FIG. 8 describes a modified embodiment of a pedal, the referencenumerals being stated only insofar as they do not refer to constructionelements which have been described already in connection with FIG. 7.

In FIG. 8 the interior of the cap 55 is filled with pressure fluid 64,which pressure fluid can be a hydraulic fluid or any suitable gas.Instead of the sensor 58 a pressure transducer 65 is arranged in theinterior of the cap 55 and comprises an elastic diaphragm 66. Thepressure transducer 65, in turn, is provided with two electricconnections 59 and 60. Said transducer is of a design such that itsinner resistance allocated to the connections 59, 60 varies with thepressure exerted on the diaphragm 66. The pressure applied by theoperator's foot to the cap 55 is transmitted through the pressure fluid64 onto the diaphragm 66, a control element being caused in turn whichbrings about a corresponding change in current via the connections 59,60 in dependence on the force exerted by the operator. It is notabsolutely necessary though that the sensor 65 changes its resistancebehaviour in consequence of the pressure variation in the pressure fluid64. It is also possible to use a transducer which, due to the pressureapplied to it, delivers a corresponding voltage to the connections 59,60 or, respectively, changes its capacity or inductivity.

FIG. 9 shows in a simplified view another embodiment of the pedalassembly which is modified in comparison to FIGS. 8 and 9. A spiralspring is inserted into the interior 67 of the cap 55 which is to servetwo purposes at the same time. On the one hand, the spiral spring 68boosts the outwardly directed force of the interior 67 on the inner surface of the cap 55. On the other hand, the spiral spring 68 isconnected--in a manner not shown--with an induction-measuring devicewhich constantly measures the inductivity of the spiral spring 68. Adeformation of the cap 55 results also in a corresponding variation ofthe coil distance of the spiral spring 68 and thus in a correspondingchange in the inductivity of this spring. This modified induction valueis measured by the non-illustrated measuring device, the measured valuerepresenting a standard for the magnitude of the control quantitydesired by the operator.

FIG. 10, in turn, shows an embodiment of the pedal assembly modified inrespect of FIGS. 7, 8 and 9, an elastic contact surface 69 being securedto the inner surf ace of the cap 55 which may be effected by cementing,vulcanizing or spraying-on, for instance.

Opposite to the contact surface 69, two semi-circular electrodes 70, 71are arranged in the bottom 57 and are shown in a top view in FIG. 10a.These electrodes 70, 71 are connected with an alarm apparatus which isillustrated symbolically as warning lamp 72 in FIG. 10.

Once the inner surf ace of the cap 55 with its contact surface 69 ismoved into contact with the electrodes 70, 71, the alarm apparatus 72will respond because of the current flow initiated e.g. by a battery 73.It can be indicated thereby for instance that the pedal assembly is nomore operable because of lack in pressure fluid so that correspondingsafety operations such as an automatic braking operation, disconnectionof the fuel supply or the like can be performed herein owing to theresponse of the alarm apparatus.

The sensors and transducers illustrated in FIGS. 7 to 10 can be combinedin that for instance two transducers and/or sensors of different typeare incorporated in one pedal assembly thereby allowing to assess theparallel prevailing signals obtained by different transducers and, owingto their redundancy, thereby achieving an enhanced safety for thecorrective signals of course the alarm contact according to FIG. 10 canalso be combined with the transducers according to FIGS. 7 to 9. It isensured by these measures that on failure of one transducer, theoperator will be given an indication as to which transducer has failed,while it is simultaneously possible to continue to issue correctivesignals via the parallel connected second transducer.

It is advantageously possible in all variants illustrated to integrateparts or even the entire hardware of a signal-processing electronicsinto the pedal assembly or, respectively, into the pedals, e.g. in thevicinity of the sensor. In FIG. 8 a printed circuit board 120 having alike electronics encompasses the sensor 65, the said electronics beingprotected mechanically by the cap.

In connection with FIG. 11 an emergency actuation is symbolically shownas it can be initiated by the inventive pedal assembly. Inside the cap55 a sensor device 74 is shown symbolically which can correspond roughlyto the sensor device according to FIG. 7 or 8. The bottom 5 7 of the capis penetrated by a channel 76 which passes over into a pressure fluidline 75. The passage of channel 76 and line 75 is adapted to bemagnetically closed or opened, respectively, by a two-way valve 77. Saidvalve 77 is operated magnetically via the sensor device 74. The sensordevice may perform the functions of the transducers and, respectively,sensors according to FIGS. 7 to 9, and it may also have the switchingability of the contact devices 69, 70 according to FIG. 10. Anotherpossibility of triggering the valve 77 by the sensor device 74 canconsist in a threshold-value switch which switches the valve 77 toassume its open position illustrated in FIG. 11 once a predefinedpressure value is reached. The following control possibility is obtainedthereby. In the normal condition the sensor device 74, as is describedwith reference to FIGS. 7 to 9, issues a corrective signal responsive tothe pressurization of the cap 55. If, for any reason whatsoever, apredefined pressure is exceeded or an action is initiated, as isdescribed with reference to FIG. 10, the magnet of the valve 11 willreact, and the pressure fluid of the interior of the cap 55 maypropagate via the valve 77 into the line 75 from where it is able todrive a suitable generator 78. Corresponding alarm devices and auxiliarydevices can be triggered by the generator 78. It thus shows that, evenupon malfunction of the sensor 74 in respect of its analogous placevalues, a corrective function is still possible by virtue of thegenerator 78 through the pressure fluid contained in the interior 64.This way a corrective action can still be performed via the generator 78even on failure of the valve 77.

If, on the other hand, the valve 77 operates in its normal condition,the valve 77 is closed and the transducer 74 can be actuated through thepressure or any other control variable within the interior 64.

Another protective function of the valve 77 resides in an emergencyfunction upon power failure. In the normal case the valve is energizedand the hydraulic effect is stopped. The system operates through thesensor 74. When the power fails, the valve will open and the pedal willoperate hydraulically.

FIG. 12 shows the possibility of controlling an auxiliary-force brakesystem, such as a brake power booster 79, in addition to FIG. 11 or alsogenerally via the cap 55 and a line 75 as well as a generator 78, withbrake lines 81, 82 emanating from the master cylinder 80 of the booster.

The pedal assembly according to the present invention offers a greatnumber of advantages. On the one hand, it is of a very straightforwarddesign. on the other hand, it is possible by such pedal assemblies topermit much more complex evaluations to be effected by the electronicsrelated to the pedal assembly than has previously been the case. Forinstance, it can be found out by an evaluating electronics by virtue ofa defined pulsewise actuation of the elastic cap 55 that the speed valueadjusted the last is to be preserved so that the vehicle speed can thenbe adjusted to adopt this value. Another advantage resides in the easeof exchanging the pedal assemblies so that these can be adjusted intheir response behaviour to different operators in that e.g. theresponse behaviour of the sensors is changed electronically, it beingpossible to adapt the pedal in a simple fashion to the more or lesssusceptible behaviour of the operator and his/her forces available forthe control.

We claim:
 1. A pedal assembly for an automotive vehicle having an energysupply and a data bus, said pedal assembly comprising:at least twopedals each having a first electrical signal generator indicating pedalposition, a second electrical signal generator also and independentlyindicating pedal position, and a third electrical signal generatorindicating when the pedal exceeds a threshold inclination; and a dataprocessing system for receiving electrical signals from each of saidplurality of electrical signal generators and delivering electricalsignals to said data bus, said data processing system having means forproviding energy from said energy supply to said pedal assembly andbeing redundant so that it can determine the consistency of saidelectrical signals.
 2. A pedal assembly as claimed in claim 1 whereinsaid data processing system comprises:a first data processing branchhaving:(a) a first multiplex unit receiving electrical signals from eachof said first electrical signal generators, (b) a first analog-digitalconvertor receiving electrical signals from said first multiplex unit,and (c) a first microprocessor receiving electrical signals from saidfirst analog-digital converter, said first microprocessor also receivingelectrical signals from each of said third signal generators; and asecond data processing branch having:(a) a second multiplex unitreceiving electrical signals from each of said second electrical signalgenerators; (b) a second analog-digital converter receiving electricalsignals from said second multiplex unit, and (c) a second microprocessorreceiving electrical signals from said second analog-digital converter,said second microprocessor also receiving electrical signals from eachof said third signal generators and exchanging data with said firstmicroprocessor to check whether one of said first microprocessor tocheck whether one of said first and said second data processing branchesis defective and, if so, which data processing branch is defective.
 3. Apedal assembly as claimed in claim 2 wherein said data processing systemfurther comprises an intersection for receiving electrical signals fromsaid first and second microprocessors and delivering electrical signalsto said data bus.
 4. A pedal assembly as claimed in claim 1 wherein saidfirst electrical signal generators are first potentiometers, said secondelectrical signal generators are second potentiometers, and said thirdelectrical signal generators are switched.
 5. A pedal assembly asclaimed in claim 4 wherein said first potentiometers and said secondpotentiometers are rotary potentiometers, each rotary potentiometerhaving an axis and at least one of a travel indicator, an angleindicator, and a digital position indicator.
 6. A pedal assembly asclaimed in claim 5 further comprising:a housing; a plurality of tensionsprings attached to said housing; a foot board associated with each ofsaid pedals, each foot board having a free end; a pulley associated witheach rotary potentiometer, each said pulley arranged on the same axis asits associated rotary potentiometer; and a belt associated with eachrotary potentiometer, each said belt secured on said free end of a footboard, engaged with said associated rotary potentiometer, and held byone of said tension springs.
 7. A pedal assembly as claimed in claim 5further comprising a screwed rod disposed between each rotarypotentiometer and its associated pedal, each said screwed rod adapted torotate upon depression of said pedal and act directly upon said rotarypotentiometer.
 8. A pedal assembly as claimed in claim 1 wherein saidenergy providing means has a stabilizer and an auxiliary accumulatorensuring that said pedal assembly can deliver a warning even uponfailure of the energy supply.
 9. A pedal assembly as claimed in claim 1further comprising:a foot board associated with each of said pedals; ahousing having at least one stop; at least one least spring arrangedbeneath each of said foot boards and clamped on said housing, each saidleaf spring engaging said at least one stop for adjusting theforce-travel characteristics of each of said pedals.
 10. A pedalassembly as claimed in claim 1 wherein each of said pedals has anadjustable heel support.
 11. A pedal assembly as claimed in claim 10wherein said adjustable heel supports are electrically operable.
 12. Apedal assembly as claimed in claim 11 wherein said automotive vehiclehas an electrically operated seat-memory element and said electricallyoperable adjustable heel supports are electrically connected with saidseat-memory element.
 13. A pedal assembly as claimed in claim 1 whereineach of said pedals has a means for adjusting the inclination of saidpedal.
 14. A pedal assembly as claimed in claim 13 wherein saidadjusting means are electrically operable.
 15. A pedal assembly asclaimed in claim 14 wherein said automotive vehicle has an electricallyoperated seat-memory element and said electrically operable adjustingmeans are electrically connected with said seat-memory element.
 16. Apedal assembly for an automotive vehicle comprising:an assembly plate;and at least two pedals each having:(a) an elastic housing mounted onsaid assembly plate and defining an internal cavity, and (b) a pressuresensor positioned in said internal cavity.
 17. A pedal assembly asclaimed in claim 16 wherein said elastic housing is a cap which, whendeformed by an external force, applies an analogous force to saidpressure sensor.
 18. A pedal assembly as claimed in claim 17 whereinsaid pressure sensor is:(a) positioned adjacent said elastic housing andat least partly fills said internal cavity defined by said housing; and(b) a block of electrically conductive rubber having pressure-responsivecurrent-voltage characteristics and two spaced electrodes.
 19. A pedalassembly as claimed in claim 17 further comprising pressure fluid andwherein:(a) said internal cavity defined by said elastic cap is pressurefluid tight and contain said pressure fluid, and (b) said pressuresensor is a pressure transducer responsive to pressure variations insaid pressure fluid caused by changes in the volume of said internalcavity.
 20. A pedal assembly as claimed in claim 19 furthercomprising:an auxiliary brake system; an actuating member connected tosaid auxiliary brake system; and a pressure fluid line connected on oneend to said internal cavity defined by said elastic cap and on itsopposite end to said actuating member, said actuating member operatingsaid auxiliary brake system in response to the pressure in said pressurefluid line.
 21. A pedal assembly as claimed in claim 20 furthercomprising a valve inserted into said pressure fluid line and responsiveto said pressure transducer said valve opening when said pressuretransducer reaches a predetermined value.
 22. A pedal assembly asclaimed in claim 17 wherein said pressure sensor is a spria spring whosedeformations create a measurable change in the indicitivity of saidspiral spring.
 23. A pedal assembly as claimed in claim 22 wherein saidelastic cap has a bottom and an inner top surface and said spiral springis a conical spiral spring having its external winding supported on saidbottom of said elastic cap and its opposite winding supported on saidinner top surface of said elastic cap.
 24. A pedal assembly s claimed inclaim 17 wherein said elastic cap has a bottom and an inner top surfaceand said pressure sensor has two contact electrodes disposed on saidbottom of said elastic cap and a contact surface disposed on said innertop surface of said elastic cap, said contact electrodes beingshort-circuited when engaged by said contact surface.
 25. A pedalassembly as claimed in claim 17 further comprising a fastener formounting said elastic housing on said assembly plate, said fastenerselected from the groups consisting of screws, welds, cements, clamps,and locks.